The performance of estimating Systolic Blood Pressure (SBP) in
anesthetized patients via Pulse Arrival Time (PAT) techniques was
studied with respect to the minimum required time in between two
recalibration procedures.
Materials: a clinical trial [NCT026515581 involving 14 patients was
conducted measuring PAT from an ECG and an arterial line inserted into
the radial artery.
Methods: comparison of BP estimates from PAT measurements against
invasive BP values was performed in terms of mean error and standard
deviation of the error (AAMI/ANSI/ISO 81060-2), cumulative percentage of
readings falling within 5, 10 and 15 mmHg (BHS criteria), and MAD Mean
Absolute Difference (IEEE Std 1708). Two calibration strategies were
explored, involving time between recalibration periods ranging from 10
seconds to 8 minutes.
Results: assuming an affine calibration function between PAT and SBP,
different slope (Mean Slope:-1.45, CI:-1.64 to -1.27 mmHg/ms) and offset
values (Mean Offset: 575, CI: 517 to 633 mmHg) were found in between
patients. In addition, given a patient, affine calibration functions at
different anesthesia phases also showed to be variable. When assessing
agreement in terms of existing international standards it was found that
PAT based SBP estimates complied with requirements when time between two
calibrations was smaller than 60 seconds.
Conclusions: the use of anesthetic agents compromises the implementation
of PAT-based techniques to estimate SBP.